/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

package axil.definition;

import axil.api.AxilObject;
import axil.etc.Compressed;
import axil.etc.Identity;
import axil.framework.localization.Namespace;
import axil.framework.validation.Validated;
import axil.framework.validation.ValidationContext;
import axil.framework.xml.InputXML;

import static axil.framework.Functions.*;


/**
 * An object representing the definition of a constant. Constants are seldom
 * used, but can be important in certain domains. For example, "e" and "pi" are
 * important concepts in trigonometry, so these make good constants. Constants
 * are defined at the module level to avoid polluting the namespace when they
 * are not wanted.
 */
public class ConstantDefinition implements Compressed, Validated, Identity {
	private static final Namespace ns = Definition.ns;

	private String name;
	private String type;
	private String text;

	private transient AxilObject value;


	public ConstantDefinition(InputXML xml) {
		name = xml.text("name");
		type = xml.text("type");
		text = xml.content();
	}


	/**
	 * Get the unique identity for this object. The string returned is never
	 * empty and contains no punctuation characters beyond a possible '-'. The
	 * value is suitable for use as an identifier.
	 */
	public String identity() {
		return name;
	}


	/**
	 * Compress this object, reducing its memory footprint as much as possible.
	 * A compressed object is still fully functional for script evaluation but
	 * may no longer possess complete metadata.
	 */
	public void compress() {
		return;
	}


	/**
	 * Validate this object in the given context. Any problems detected with the
	 * correctness or completeness of this object are placed into the context.
	 * This method descends into its owned members, validating them as well.
	 */
	public void validate(ValidationContext context) {
		context.check("name", identifier(name), msg(ns, "constant-name"));
		context.check("type", ! empty(type), msg(ns, "constant-type"));
		try {
			value = typeof(type).parse(text.trim());
		} catch (Exception e) {
			context.error(msg(ns, "type-conversion", nv("value", text)));
		}
	}


	public AxilObject value() {
		assert value != null;
		return value;
	}
}
